Not applicable.
1. Field of the Invention
The present invention relates generally to disk drives, and in particular to a disk drive having a rotary actuator with a thermo-conductive coil support element.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes the disk drive base, a cover, at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA).
The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base. The spindle motor hub has an outer hub flange that supports a lowermost one of the disks. Additional disks may be stacked and separated with annular disk spacers that are disposed about the spindle motor hub. The head stack assembly has an actuator assembly including at least one air bearing slider or head, typically several, for reading and writing data from and to the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached sliders are moved relative to tracks disposed upon the disk.
The head stack assembly includes the actuator assembly, at least one head gimbal assembly (HGA), and a flex circuit cable assembly that are attached to the actuator assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body, a pivot bearing cartridge, one or more actuator arms that extend from one side of the actuator body, and a coil portion that extends from an opposite side of the actuator body. The actuator body includes a bore and the pivot bearing cartridge engaged within the bore for allowing the actuator body to rotate between limited positions. The coil portion includes a coil that is configured to interact with one or more permanent magnets to form a voice coil motor.
At least one head gimbal assembly is distally attached to each of the actuator arms. A head gimbal assembly includes an air bearing slider that is attached to a suspension with a gimbal. The suspension resiliently supports the slider above the tracks of the disk during operation of the disk drive facilitating the slider to xe2x80x9cflyxe2x80x9d above the disk. The head gimbal assemblies and the flex circuit cable assembly are attached to the actuator assembly. The voice coil motor is configured to allow the actuator assembly to be controllably rotated or pivoted so as to move the sliders relative to the disks for reading and writing operations with respect to the tracks contained on the disks. The printed circuit board assembly is disposed in electrical communication with the coil via the flex circuit cable assembly for providing a control current to energize the coil to create an electromagnetic field that interacts with the permanent magnets to controllably position the actuator assembly.
A topic of concern is to reduce read/write access time (the time required to position the transducer head from an operable position adjacent a particular track to another track to perform read/write operations). A low read/write access time may be achieved by increasing the strength of the magnetic field of the voice coil motor and having a high level of current applied to the coil (to produce high torque). A high level of current through the coil, however, results in a relatively higher power consumption. If heat produced in the coil is not dissipated at a rapid enough rate, then the coil temperature increases which in turn increases the coil resistance. This in turn counterproductively reduces the coil current increasing the access time. Moreover, elevated coil temperatures may result in damage to the coil and adjacent components. An additional topic of concern is the desire to reduce the overall disk drive size, and in particular the reduction of the height of the disk drive. In this regard, there is a need in the art for an improved actuator assembly design that takes into consideration vertical height limitations and provides thermal heat transfer from the coil of the voice coil motor, so as to reduce the accumulation of heat energy in the coil to reduce the coil operating temperature.
An aspect of the present invention can be regarded as a disk drive that includes a disk drive base and a rotary actuator coupled to the disk drive base. The rotary actuator includes an actuator body including a bore defining a longitudinal axis. The rotary actuator further includes a coil portion including a coil and a coil support element for supporting the coil. The coil support element is integrally formed with the actuator body and radially extends from the actuator body. The support element has a coil supporting surface generally perpendicular to the longitudinal axis. The coil is attached to the coil supporting surface. The coil support element is sized and configured to support the coil and formed of a thermo-conductive material for dissipating heat from the coil.
According to various embodiments, the coil support element may include an opening formed through the coil support element and the coil is disposed about the opening. The coil support element may be generally planar. The coil may be attached to the coil support element with adhesive. The coil support element and the actuator body may be formed of a metal material, such as aluminum. The rotary actuator may further include an actuator arm radially extending from the actuator body opposite the coil portion, and the actuator arm may be integrally formed with the coil support element.
According to another aspect of the present invention, there is provided the head stack assembly including the rotary actuator as described above.